local robot = require("robot")
print("Robot tree farm started")

-- Select the first slot, which is supposed to have a sapling.
robot.select(1)

-- Change these to change the tree farm grid size or the distance between each tree in the grid.
local treesX = 6
local treesZ = 6
local distanceBetweenTrees = 3

-- Goes forward eventually, no matter if something is blocking the path at the moment.
local function GoForward()
    while true do
        local movedSuccessfuly = robot.forward()
        if movedSuccessfuly then
            break
        end
    end
    robot.suck()
end

-- Goes down eventually, no matter if something is blocking the path at the moment.
local function GoDown()
    while true do
        local movedSuccessfuly = robot.down()
        if movedSuccessfuly then
            break
        end
    end
end

-- Checks for a tree
local function CheckForTree()
    -- Check for a block
    if robot.detect() then
        robot.up()

        -- Attempt to detect a block above which will determine if the tree has grown.
        local blockFound = robot.detect()
        robot.down()

        -- Check tree has grown and if so then go up.
        if blockFound then
            for blocksToMoveUp = 1, 8 do
                -- Destroy the wood in front of the robot
                robot.swing()

                -- Check if there is a block above and if so then destroy the block.
                if robot.detectUp() then
                    robot.swingUp()
                end

                -- Go up
                robot.up()
            end

            -- Move back down again
            for blocksToMoveDown = 1, 8 do
                GoDown()
            end

            -- Suck up stuff and go forward
            robot.suck()
            robot.suckUp()
            robot.suckDown()
            GoForward()

            -- Suck up stuff
            for rotation = 1, 4 do
                robot.turnLeft()
                robot.suck()
            end

            -- Go back
            robot.turnAround()
            GoForward()
            robot.turnAround()

            -- Place the new sapling here
            robot.place()
        end
    else
        -- There is no block here, place the sapling
        robot.place()
    end
end

-- Scans a row of trees.
local function CheckRowOfTrees()
    -- Check for trees in the X row.
    for treeX = 1, treesX do
        CheckForTree()

        -- If this isn't the last tree in the row then move to the next tree in the row.
        if treeX < treesX then
            robot.turnRight()
            for blocksToMove = 1, distanceBetweenTrees do
                GoForward()
            end
            robot.turnLeft()
        end
    end

    -- Go back to the first tree in the row.
    robot.turnLeft()
    for blocksToMove = 1, distanceBetweenTrees*(treesX - 1) do
        GoForward()
    end
    robot.turnRight()
end

-- Do the complete cycle.
while true do
    -- Go to each X row in the grid.
    for treeZ = 1, treesZ do
        CheckRowOfTrees()

        -- If this isn't the last X row in the grid then go to the next X row in the grid.
        if treeZ < treesZ then
            robot.turnRight()
            GoForward()
            robot.turnLeft()
            for blocksToMove = 1, distanceBetweenTrees do
                GoForward()
            end
            robot.turnLeft()
            GoForward()
            robot.turnRight()
        end
    end

    -- Go back to the starting position.
    robot.turnRight()
    GoForward()
    robot.turnRight()
    for blocksToMove = 1, distanceBetweenTrees*(treesZ - 1) do
        GoForward()
        robot.suck()
    end
    robot.turnRight()
    GoForward()
    robot.turnRight()

    -- Sleep for five seconds.
    os.sleep(5)
end